Pointer instrument

ABSTRACT

In a pointer-type instrument ( 1 ) having a pointer with a pointer shaft ( 5 ) that deflects a pointer vane ( 2 ), power is supplied to a light source ( 3 ), which is connected to the pointer for rotation in common, by a flexible, spiral film ( 11 ) provided with conductor tracks ( 12, 13 ). For this purpose, the pointer shaft ( 5 ) has an enlargement ( 9 ), which supports the film ( 11 ) and secures it against sliding off axially. As a result, the film ( 11 ) can be made particularly thin, thereby making it possible to reduce the driving torque required to deflect the pointer shaft ( 5 ).

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a pointer-type instrument, in particular for amotor vehicle, having a pointer with a pointer shaft that deflects apointer vane and having a light source connected to the pointer forrotation in common, the light source being connected to a power supplyby means of a flexible film provided with conductor tracks.

A pointer instrument of this kind, in which, in addition, the lightsource is arranged in an upper portion of the pointer shaft and shineslight directly into the pointer vane, is widely used especially in theautomotive industry today and is thus part of the prior part. In thisarrangement, a film with printed-on conductor tracks is connected at oneend to a circuit board and at its other end to contact locations on theshaft, where it forms a loop.

Here, there is a disadvantageous effect due to the fact that, when thepointer is deflected, the loop formed by the film jumps each time thereis a reversal in the movement of the pointer, owing to the large angleof pointer rotation required and the intrinsic stiffness of the film.This results in torque jumps, which lead to inaccuracy of the display.Moreover, the characteristic of the restoring torque of a pointer-typeinstrument of this kind is nonuniform, further impairing its accuracy ofindication. The pointer drive must therefore produce a high drivingtorque to enable the torques produced by the film to be absorbed and toensure accurate indication.

These abovementioned disadvantageous effects due to the spring action ofthe film could be reduced by making the film as long and thin aspossible. In practice, however, this has the effect that the film slidesoff axially relative to the pointer shaft due to its low dimensionalstability and thereby impairs the operation of the pointer-typeinstrument.

SUMMARY OF THE INVENTION

The problem underlying the invention is to provide a pointer-typeinstrument of the type stated at the outset such that the driving torquerequired to deflect the pointer shaft is significantly lower incomparison with known pointer-type instruments. At the same time,fluctuations in the restoring torque should to a large extent beavoided.

According to the invention, this problem is solved in that the film canbe wound in a spiral onto the pointer shaft, and that the pointer shafthas a flange-like enlargement, which extends in an essentially radialdirection away from the pointer shaft, against which the film can beplaced by one of its lateral edges and the outside diameter of which isat least as great as the wound-on diameter of the film.

The flange-like enlargement of the pointer shaft prevents the film fromsliding off axially in an effective manner by supporting the film. Thisallows the film to be made considerably thinner in comparison with knownpointer-type instruments, and this is associated with a reduction in therestoring forces. The driving torque required to drive the pointer shaftis thus considerably reduced. It is furthermore possible to reduce thenumber of turns required to give a uniform resistance torquecharacteristic, and the total length of the film and hence productioncosts are thus lower.

If, according to an advantageous development of the invention, thepointer vane is a light guide that can be illuminated, and light emittedby the light source can be coupled into the pointer vane, thepointer-type instrument can be read particularly easily, especially inthe dark.

It is also advantageous if the light source is arranged on the pointervane and light can be emitted in the direction of a viewer by the lightsource. In this context, the pointer vane can be designed as a simpleweb, on which the light source is mounted. To increase luminosity andimprove the readability of the pointer, a plurality of light sourcesarranged adjacent to one another in the longitudinal direction of thepointer vane can be provided.

A particularly clearly divided and comprehensible pointer-typeinstrument is obtained if, according to another advantageous developmentof the invention, a dial, at least partial areas of which can betransilluminated, is arranged in front of that side of the pointer whichfaces a viewer. From the point of view of the viewer, the pointer ishere arranged behind the dial but can be seen through those areas of thedial that can be transilluminated. Visibility is particularly good ifthe pointer is actively illuminated by means of the light source.

A particularly advantageous embodiment of the invention is obtained ifthe flange-like enlargement is embodied as a circular disk. Such arotationally symmetrical embodiment of the enlargement ensures that thefilm is wound on uniformly and hence in a manner that reduces stress onthe film with its conductor tracks. It is thereby possible to furtherreduce the susceptibility of the pointer-type instrument thus. equippedto faults.

In a particularly advantageous development of the invention, theflange-like enlargement has an oblique surface which falls away outward.By means of this oblique surface in the form of a kind of ramp, it ispossible to considerably simplify the wind-on process during the rotarymotion of the pointer shaft. In this case, it is possible to increasethe tolerances between the film and the enlargement without thesimultaneous risk that the film will be wound on nonuniformly or willslip off over the edge of the enlargement.

Another, particularly advantageous embodiment of the invention isobtained if, in addition to the first enlargement, the pointer shaft hasa second enlargement and the film is arranged between the enlargements.This makes it possible to achieve a further improvement in guidance,thus excluding the possibility that the film will slip off at the topand, in association with this, strike against other components of thepointer-type instrument under the influence of external forces, e.g.vehicle movements.

Another, particularly advantageous development of the invention isobtained if in an end region remote from the pointer shaft, the film hasa portion which is thicker than in a central region, which can be woundup. A film thickness of approximately 75 μm in its central wind-onregion and of approximately 300 μm in its end regions is advantageous,for example, thereby achieving a higher mechanical robustness in thelatter regions. By stiffening the film in this way, it is possible toachieve dimensional stability in that portion which is not wound upduring the rotary motion of the pointer shaft. Moreover, there is notendency for the film to sag outside those areas which are supported bythe enlargement. There is therefore no need for further guide means.

In this context, a particularly advantageous development of theinvention is obtained if the light source is a light-emitting diode thatis brought into contact with the film. A unit of this kind, which hasalready been preassembled, comprising the film and the illuminationmeans embodied as a light-emitting diode, significantly reduces theoutlay on assembly. In this case, contact-making errors during assemblyare virtually eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention admits of various embodiments. To illustrate its basicprinciple further, two of these are illustrated in the figures of thedrawing and described below. In the drawing:

FIG. 1 shows a lateral, partially sectioned representation of apointer-type instrument according to the inventions; and

FIG. 2 shows part of a pointer shaft of another pointer-type instrumentaccording to the invention with two enlargements.

FIG. 3 shows the dial being in front of the pointer of the pointer-typeinstrument of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 gives a simplified representation of a pointer-type instrument 27with a pointer 1 having a pointer vane 2. Shining into this pointer vane2 is a light source 3, which is provided as a light-emitting diode andis shielded from a possible viewer by a cap 4. At its end opposite apointer tip 28, the pointer vane 2 is connected on the underside to apointer shaft 5, which is passed through a dial 6 and can be deflectedby means of a pointer drive 7 embodied as a measurement mechanism.Between a circuit board 8 carrying the pointer drive 7 and the dial 6,the pointer shaft 5 has a flange-like enlargement 9, which has anoblique surface 10 that falls away outward. Resting against theenlargement 9 is part of a wind-on central region 26 of a film 11, whichis wound around the pointer shaft 5 in a spiral and has a lower lateraledge 29. The film 11, which is provided with two conductor tracks 12, 13for connecting the light source 3 to an energy supply, is passed to theoutside approximately at right angles to the pointer shaft 5 and, in itsend region remote from the pointer shaft 5, has a thickened portion 14,which points downward. This thickened portion 14 has a plug-in connector15, by means of which the film 11 is connected to the circuit board 8forming the power supply. The integral connection of the film 11 to thelight-emitting means 3, said connection running along a recess in thepointer shaft 5, is not shown.

FIG. 3 shows the pointer-type instrument of the present invention asdepicted in FIG. 1 with the dial being in front of the pointer.

FIG. 2 shows a perspective representation of part of a pointer shaft 16in an embodiment which has been modified in comparison with the pointershaft illustrated in FIG. 1. Here, the pointer shaft 16 has twoenlargements 19, 20 arranged mirror-image fashion and each embodied as acircular disk 17, 18. These enlargements enclose a film 21, likewiseshown only in part, with two conductor tracks 22, 23, the film havingbeen completely unwound in the position illustrated. If the light source(not shown here) is, for example, a color-changing light-emitting diode,the color of which is changed when a limiting value is reached, forexample, more than two conductor tracks may be necessary. To allowbetter guidance of the film 21, the two circular disks 17, 18 each havean oblique surface 24, 25 which falls away outward.

We claim:
 1. A pointer instrument comprising a pointer with a pointershaft, said shaft being rotatable relative to a stationary part of theinstrument for deflecting a pointer vane of the pointer, a light sourceconnected to the pointer for rotation in common, the light source beingconnected to a power supply by a flexible film provided with conductortracks, wherein the film (11, 21) is windable in a spiral onto thepointer shaft (5, 16), and wherein the pointer shaft (5, 16) has aflange-like enlargement (9, 19, 20) for guiding the film, saidenlargement extending in an essentially radial direction away from thepointer shaft (5, 16), said film being windable on said shaft betweenthe enlargement and the pointer and placeable against the enlargement byone of its lateral edges, the enlargement having an outside diameterwhich is at least as great as the wound-on diameter of the film (11,21), wherein in an end region of said film remote from the pointer shaft(5, 16), the film (11, 21) has an upstanding portion (14) extending fromsaid stationary part, which upstanding portion is thicker than said filmin a central region (26), which central region is windable on saidpointer shaft.
 2. The pointer instrument as claimed in claim 1, whereinthe pointer vane (2) is a light guide that is illuminable, and whereinlight emitted by the light source (3) is couplable into the pointer vane(2).
 3. The pointer instrument as claimed in claim 1, wherein the lightsource is arranged on the pointer vane, and wherein light is emittableby the light source in a direction of a viewer.
 4. The pointerinstrument as claimed in claim 1, wherein a dial, at least partial areasof said dial being transilluminable, is arranged in front of a side ofthe pointer which faces a viewer.
 5. The pointer instrument as claimedin claim 1, wherein the flange-like enlargement (9, 19, 20) is acircular disk (17, 18).
 6. The pointer instrument as claimed in claim 1,wherein the flange-like enlargement (9, 19, 20) has a first non-beveledregion surrounding the pointer shaft and a second beveled region arounda periphery of said first region.
 7. The pointer instrument as claimedin claim 1, wherein, in addition to the first-mentioned enlargement (19,20), the pointer shaft (5, 16) has a second enlargement (19, 20), andwherein the film (21) is arranged between said enlargements (19, 20). 8.The pointer instrument as claimed in claim 1, wherein the light source(3) is a light-emitting diode, said light-emitting diode being incontact with the film (11, 21).
 9. A pointer instrument for a motorvehicle comprising a pointer with a pointer shaft, said shaft deflectinga pointer vane of the pointer, a light source connected to the pointerfor rotation in common with the pointer, the light source beingconnected to a power supply by a flexible film provided with conductortracks, wherein the film (11,21) is windable in a spiral onto thepointer shaft (5,16), and wherein the pointer shaft (5,16) has aflange-like enlargement (9, 19, 20) for guiding the film, saidenlargement extending in an essentially radial direction away from thepointer shaft (5, 16), said film being windable on said shaft betweenthe enlargement and the pointer and placeable against the enlargement bya lateral edge of the film, the enlargement having an outside diameterwhich is at least as great as the wound-on diameter of the film (11,21), wherein in an end region of said film remote from the pointer shaft(5, 16), the film (11, 21) has an upstanding portion (14) extending fromsaid stationary part, which upstanding portion is thicker than said filmin a central region (26) of the film, which central region of the filmis windable on said pointer shaft.